Module: Ramaze::Helper::CSRF

Includes:
Innate::Optioned
Defined in:
lib/ramaze/helper/csrf.rb

Overview

A relatively basic yet useful helper that can be used to protect your application from CSRF attacks/exploits. Note that this helper merely generates the required data, and provides several methods. You still need to manually add the token to each form.

The reason for this is because this is quite simple. Ramaze is meant as a framework that works with any given helper, ORM, template engine and so on. If we were to automatically load this helper and include (a perhaps more advanced) CSRF system that would mean that every form helper, official or third-party, would have to support that specific system. However, there’s no need to panic as it’s very easy to setup a basic anti CSRF system.

## Usage

In order to enable CSRF protection we need to do two things. Load the helper and create a before_all block in a controller. Take a look at the following code:

class BaseController < Ramaze::Controller
  before_all do
    puts "Hello, before_all!"
  end
end

This would output “Hello, before_all!” to the console upon each request. Not very useful but it does show what the before_all block can do. On to actual CSRF related code!

class BaseController < Ramaze::Controller
  before_all do
    csrf_protection :save do
      # ....
    end
  end
end

This example introduces an extra block that validates the current request. Whenever a user requests a controller that either extends BaseController or has it’s own before_all block Ramaze will check if the current request data contains a CSRF token. Of course an if/end isn’t very useful if it doesn’t do anything, let’s add some code.

class BaseController < Ramaze::Controller
  before_all do
    csrf_protection :save do
      puts "Hello, unsafe data!"
    end
  end
end

The code above checks if the current method is “save” (or any other of the provided methods) and checks if an CSRF token is supplied if the method matches. Protected methods require a token in ALL HTTP requests (GET, POST, etc). While this may seem weird since GET is generally used for safe actions it actually makes sense. Ramaze stores both the POST and GET parameters in the request.params hash. While this makes it easy to work with POST/GET data this also makes it easier to spoof POST requests using a GET request, thus this helper protects ALL request methods.

If you’re a lazy person you can copy-paste the example below and adapt it to your needs.

class BaseController < Ramaze::Controller
  before_all do
    csrf_protection :save do
      respond("The supplied CSRF token is invalid.", 401)
    end
  end
end

Instance Method Summary collapse

Instance Method Details

#csrf_protection(*methods, &block) ⇒ Object

Method that can be used to protect the specified methods against CSRF exploits. Each protected method will require the token to be stored in a field called “csrf_token”. This method will then validate that token against the current token in the session.

Examples:

# Protect "create" and "save" against CSRF exploits
before_all do
  csrf_protection :create, :save do
    respond("GET TO DA CHOPPA!", 401)
  end
end

Parameters:

  • methods (Array) —

    Array of method names that should be checked.

  • block (Proc) —

    Block that will be executed if the token is invalid.



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# File 'lib/ramaze/helper/csrf.rb', line 102

def csrf_protection(*methods, &block)
  if methods.include?(action.name) \
  or methods.include?(action.name.to_sym)
    unless validate_csrf_token(request.params[CSRF.options.field_name])
      yield
    end
  end
end

#generate_csrf_token(args = {}) ⇒ Object

Generate a new token and create the session array that will be used to validate the client.

Note that this method will be automatically called if no CSRF token exists.

Parameters:

  • args (Hash) (defaults to: {}) —

    Additional arguments that can be set such as the TTL.



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# File 'lib/ramaze/helper/csrf.rb', line 121

def generate_csrf_token(args = {})
  random = SecureRandom.random_bytes(512)
  time   = Time.now.to_f
  token  = Digest::SHA512.hexdigest(random + time.to_s)

  # Time to store all the data we want to check later.
  session[:_csrf] = {
    :token => token,
    :ip    => request.ip,
    :agent => request.env['HTTP_USER_AGENT'],
    :host  => request.host
  }

  return
end

#get_csrf_token ⇒ String

Retrieves the current value of the CSRF token.

Examples:

form(@data, :method => :post) do |f|
  f.input_hidden :csrf_token, get_csrf_token()
end

Returns:

  • (String) —

    The current CSRF token.



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# File 'lib/ramaze/helper/csrf.rb', line 146

def get_csrf_token
  if !session[:_csrf] || !self.validate_csrf_token(session[:_csrf][:token])
    self.generate_csrf_token
  end

  return session[:_csrf][:token]
end

#validate_csrf_token(input_token) ⇒ TrueClass|FalseClass

Validates the request based on the current session date stored in _csrf.

Examples:

before_all do
  if validate_csrf_token(request.params['csrf_token']) != true
    respond("Invalid CSRF token", 401)
  end
end

Parameters:

  • input_token (String) —

    The CSRF token to validate.

Returns:

  • (TrueClass|FalseClass) 


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# File 'lib/ramaze/helper/csrf.rb', line 167

def validate_csrf_token(input_token)
  # Check if the CSRF data has been generated and generate it if this
  # hasn't been done already (usually on the first request).
  if !session[:_csrf] or session[:_csrf].empty?
    self.generate_csrf_token
  end

  _csrf = session[:_csrf]

  valid = session[:_csrf][:token] == input_token &&
    _csrf[:host]  == request.host &&
    _csrf[:ip]    == request.ip &&
    _csrf[:agent] == request.env['HTTP_USER_AGENT']

  if valid
    generate_csrf_token

    return true
  else
    return false
  end
end